Round balers have become quite prevalent for their capability of producing a conveniently sized cylindrical bale, very often automatically wrapped with a sheeting material such as net or film. The round balers generally have a bale-forming chamber defined by a pair of spaced-apart side walls and a plurality of parallel belts trained around a plurality of rolls spanning between the side walls. A pick-up mechanism picks up crop material, such as hay, from the ground as the baler travels across the field, and is fed into a fixed or expandable chamber where it is rolled up to form a compact cylindrical hay package. While still inside the bale-forming chamber in its compacted form, the outer surface of the package is wrapped with twine or other wrapping material, such as film or net, prior to ejection of the wrapped bale from the chamber onto the ground for subsequent handling.
In a round baler of this type, there exists a belt tracking problem. When crop enters in between the belts, it tends to wrap around the roller and to cause sideway displacement of the belt. When adjacent belts come into contact with each other, the friction leads to substantial wear of the belts. Various attempts have been made to solve the belt tracking problem. These belt tracking problems are especially relevant as the round baler comprises a plurality of rather narrow parallel belts which are arranged close to each other. When the parallel path of the belts is not sufficiently assured, adjacent belts risk interference or entanglement with each other.
A European patent application EP2272320 presents a drive roller for flat belts, wherein the roller comprises lagging with grooves substantially non-parallel to the direction of travel of the belt, e.g. in a herringbone pattern. The grooves provide path for moisture or foreign material to be displaced from the driving surface between the roller and the flat belt.
A UK patent application GB2201630 relates to a baling machine in which the rolls are provided with rubber collars with continuous grooves therein, in the form of rings, which converge toward their bases. There are 10 to 200 grooves per 10 mm length of collar. The plurality of narrow grooves enable liquid to escape from the driving surface between the roller and the flat belt. A U.S. Pat. No. 5,213,202 presents a similar approach, wherein the rollers comprise opposed helical grooves.
A U.S. Pat. No. 5,941,168 presents a baler with full-width belts, extending substantially a transverse distance from one of the side walls of the bale-forming chamber to the other of the side walls. A roller for guiding the belt is provided with a helix structure wherein the helix acts as an auger to convey debris away from the center and toward the ends of the roller. The belt may have a set of cleats extending transversely across the inner surface of the belt to engage and sweep forage material toward the helix on the respective roller, and also to help break up the material.
A U.S. Pat. No. 4,428,282 presents a baler with rollers having a plurality of sleeves thereon, each underlying a respective one of the belts and supporting the longitudinal edges of the flat belts out of contact with the core of the roller, to reduce the tendency of the roller to become wrapped with crop material. A similar approach is presented in a U.S. Pat. No. 5,749,289.
A German utility model DE20110054 presents a round baler with rollers having a plurality of sleeves which are narrower than the belts. The sleeves of one roller are shifted with respect to the sleeves of another roller, such as to effect a belt running correction.
A German utility model DE7513533 presents a round baler with rollers having spherical protrusions which are configured to lift up the central part of the belt and to keep the belt positioned on the protrusion.